Probably because they are annoyed that they are only there because of their race and sex. If Obama was white, he would not be a potential nominee.

Lol...why do think that was?

Personnaly, from what little I've followed the US election, it seems that both of them are very charismatic. Hilary has a following due to having been the first lady(not sure what her actual politics are), and Obama has really appealed to the younger crowd, being a younger, out-going candiate.

Maybe the fact of race/sex has something to do with for some people, but perhaps so just see them as not being the "typical" politican.

As I said, I haven't really looked into what their campaigns are based on, but they seem far more personable then most of the other candiates.